Power-to-weight ratio (PWR) is a performance metric that is simple to calculate, but also easy to misuse. Individually, tracking PWR over time reflects the combined effect of changes in fitness level (power output) and bodyweight. Between two riders, PWR may predict one cyclist’s potential advantage on specific terrain. And across a population of cyclists, PWR can be used to group riders of similar performance levels. On the other hand, PWR can also lead to excessive focus on both bodyweight and the weight of equipment. Here’s how to calculate, apply, and improve power-to-weight ratio.
What is Power-to-Weight Ratio in Cycling?
To calculate power-to-weight ratio, divide a cyclist’s power output in Watts by the rider’s weight in kilograms. In other words, a cyclist who produces 250 Watts and weighs 70 kilograms would have a PWR of 250 / 70 = 3.57 W/kg.
However, it is important to remember that PWR is not a static number. Rather, it’s a number that corresponds with a specific time or intensity. For instance, a highly trained cyclist might produce 5.5 Watts/kg for 30 minutes. That same rider would have a lower PWR over 60 minutes, like 4.5 W/kg. On the other hand, PWR increases for shorter efforts. Our example rider could perhaps sustain 6.0 W/kg for 15 minutes.
Power-to-weight ratio can also be calculated to correspond to a given intensity level. One of the most common ways indoor cycling apps (Zwift, RGT, etc.) categorize riders for virtual group rides and races is through “power-to-weight ratio at Functional Threshold Power (FTP)”. FTP is the highest average power output a cyclist can maintain for 60 minutes. (Read more about FTP and FTP Tests). On an individual basis, cyclists and coaches use FTP to establish training intensity ranges and evaluate training progress.
What is a good power-to-weight ratio?
Power-to-weight ratio generally increases with fitness and experience. Dr. Andy Coggan aggregated data to describe common power profiles that are conducive to success in certain cycling disciplines. As you might expect, novice cyclists have lower PWR values at FTP (2.0-2.5 W/kg). Experienced age-group competitors are a big higher (3.0-4.0 W/kg). PWRs for high-level age-group competitors are likely to be 4.0-4.75 W/kg). Naturally, elite amateurs and professional cyclists have the highest power-to-weight ratios (5.0-6.0+ W/kg).
Coggan’s power profile table differentiates between male and female PWR ranges. This is often attributed to differences in body composition between males and females. In practice, there is a lot of individual variability and overlap in cyclists with similar training and experience.
Regardless of the number, it’s important to recognize there’s much more to performance than PWR. A “good” or “great” PWR ratio doesn’t mean much without cycling skills, tactical savvy, a solid nutrition strategy, and a winning mindset. PWR is best thought of as another metric you can use to create goals for improvement.
Power-to-weight ratio and power profiling
The fact PWR changes with exercise duration is the basis for power profiling in cycling. Using a variety of testing protocols or data from competition files, coaches create a power profile by recording a rider’s highest average power output for 5 seconds, 1 minute, 5 minutes, 20 minutes, and 60 minutes.
A cyclist’s power profile can help identify strengths, weaknesses, and opportunities for improvement. These power values are converted to PWRs to track the effects of an individual athlete’s training adaptations and weight changes. Power profiles can also be compared across large groups of athletes.
How power-to-weight ratio affects cycling performance
Larger cyclists often produce more power than smaller riders because they have more mass they can use to generate force. On the other hand, lighter riders have less inertia to overcome when trying to get their smaller mass moving.
Power-to-weight ratio affects performance on all types of terrain, but it is easiest to illustrate by comparing uphill cycling performances between two riders. For example: Rider A weighs 76 kg and averaged 275 watts for a 20-minute climb, so his PWR for 20 minutes is 3.6 watts/kg. Rider B weighs 55kg and averaged 210 watts for the same 20-minute climb and has a PWR of 3.8 watts/kg. Despite producing far less power, the 55-kg rider would be further up the climb after 20 minutes. Or put another way, Rider B should be able to drop Rider A.
Is Lighter Always Better?
Not necessarily. PWR is a balance. Cyclists benefit from being light because moving a larger body takes more energy. On the other hand, adequate muscle mass and body fat are necessary for generating more power and staying healthy. From a coaching perspective, we encourage almost all cyclists to prioritize fitness and power production over bodyweight. In our experience with amateur and age group athletes, it is better to be a stronger rider who is 2-5 kilograms heavier than a lighter rider who hasn’t improved power output as much.
Excessive weight loss, and sometimes just excessive focus on bodyweight without actual weight loss, puts athletes at risk. Extremely light athletes struggle to maintain consistent high-quality training sessions. Inadequate energy consumption hinders post-exercise recovery and physiological adaptation to training. And athletes may be more susceptible to illness because they’re not providing their bodies with enough energy to support immune function.
Athletes who restrict caloric intake and/or train excessively are also at increased risk for Relative Energy Deficiency in Sport (RED-s). Furthermore, these behaviors and the beliefs behind them can increase the risk of disordered eating.
Which Is More Important, Losing Weight or Gaining Power?
For novice cyclists and experienced riders who are carrying around more than 10 extra kilograms, losing weight and gaining power are equally important and equally achievable. This also means that heavier cyclists can make bigger improvements in their PWR because they have more room to attack both parts of the equation.
Let’s use a local Colorado Springs climb as an example. Cheyenne Canyon is a 5-kilometer climb with an average 8% grade. Our example rider weighs 75kg with a max sustainable power of 250 watts. Dropping 2.5 kilograms (roughly 5 pounds) with a power output of 250 watts would cut 38 seconds off this rider’s time. Improving power output by 10 watts without any weight loss cuts 41 seconds off his time. This increases to 85 seconds if you improve power output by 20 watts. When you combine losing 2.5 kilograms of bodyweight with a 20-watt increase in sustainable power (both of which are attainable for most cyclists), this rider would go 2:03 faster up Cheyenne Canyon.
Pro cyclists have pretty much maxed out both sides of the PWR equation and they are just about as lean and as powerful as possible. On major climbs, though, that’s why other factors like hydration status, core temperature regulation, and even positioning in the group make such a difference. If a rider can stay cool, stay hydrated, and avoid unnecessary accelerations then he may have more power in reserve to take advantage of his PWR at a crucial time.
When is it better to be a heavier cyclist?
Aerodynamics are more important on flat ground and at higher speeds compared to mountain climbs and slower speeds. A cyclist’s frontal area, a big component of a rider’s aerodynamic drag, doesn’t increase linearly with body size or weight. In other words, a rider who is twice as heavy doesn’t have twice the frontal area in a cycling position.
Larger/heavier riders have an advantage on flat ground and at high speeds because they have the mass to produce more power. Compared with smaller riders, the difference in absolute power output is greater than the difference in aerodynamic drag.
In contrast, time trial bikes and wheels are heavier than bikes used in the mountains because the aerodynamic advantages are greater than the disadvantages from the added weight.
Frequently Asked Questions About Power-to-Weight Ratio
Where Does Power-to-Weight Ratio Make the Biggest Difference?
Power-to-weight ratio makes a difference anytime you accelerate, which is why even large sprinters try to stay lean, too. For the climbers, PWR is most crucial at the steepest parts of big climbs. When the grade is steep, having a higher PWR gives you the ability to accelerate more sharply, which means it provides the opportunity to launch scorching attacks. Riders with lower PWR values can’t accelerate as quickly but may be able to reel you back in when the climb is less severe.
Does Power-to-Weight Ratio Change Throughout the Year?
Yes, and that’s perfectly normal. Elite racers aim to be as strong as possible when they are also as light as they can be. However, that is a delicate balance that can’t be maintained for very long. Gaining weight or losing power means a lot of work to get back to your peak. Therefore, elite athletes try to keep fluctuations in either bodyweight or power output relatively small. Experienced amateur cyclists can expect to see a 15% change from the lowest to highest PWR they see during the year.
Does the Weight of the Bike Get Factored In?
Not typically. At the pro level of cycling the assumption is that the bikes weigh the UCI limit of 6.8 kilograms. In principle, cutting weight on the bike will effectively increase your PWR. However, factoring in bike weight encourages athletes to “buy” their way to their goal PWR. That means they often stop working to optimize power output and bodyweight. For most people, it’s better to maximize PWR regardless of the bike, and then consider weight-savings on the bike as an added race-day advantage.
Does Power-to-Weight Ratio Stay Constant During a Grand Tour Like the Tour de France?
No. Remember, PWR is not a static number. It depends on the duration of the climb, how many hours of racing have been done before that specific climb, how aggressively a particular stage or climb is contested, wind direction, temperature, and even humidity. As riders get tired, overheated/chilled, or dehydrated, PWR goes down. A climb with moderate temperatures, a tailwind, and aggressive racing can result in high PWR values. By the final climbs of long stages and the last mountain stages of the race, even the leaders’ PWRs can drop to around 5 watts/kilogram. In early mountain stages – or for shorter periods within later climbs – they will be around 6 watts/kg.